This invention relates to electronic circuit testing methods and apparatus, and more particularly to lowering the cost of such methods and apparatus while still maintaining a high degree of test capability.
Electronic circuit testers are well known in the art and are frequently designed to be general-purpose devices. This often means that each channel of the tester has the capability to provide very precise signals with very precise timing. For example, signal timing may be controllable to 0.1 nanosecond in each tester channel. Because of the complexity of the circuitry required to produce such precisely controlled testing, each channel of prior art testers may cost from $3000 to $6000. Modern integrated circuits may have hundreds of terminals (pins) to which signals must be applied and/or from which signals must be output in order to test the circuit. Because each terminal of the circuit being tested typically requires a separate tester channel, it is not uncommon for testers to cost hundreds of thousands of dollars, or even in excess of a million dollars.
The complexity of the channel circuitry of many prior electronic circuit testers also means that their overall control circuitry must be relatively complex. For example, extremely high speed test vector memories may be needed to supply successive test vectors at the rate required to keep up with desired test speeds. Whereas for reasons of economy it might be desirable to use a computer of the relatively low cost personal computer class to control an electronic circuit tester, this has often not been possible because the demands of prior testers for extremely high speed and high precision have exceeded the capabilities of personal computers for control.
In view of the foregoing it is an object of this invention to provide highly capable electronic circuit testers which have much lower cost than many prior testers.
It is a more particular object of this invention to provide electronic circuit testers which lend themselves to operation by computers of the personal computer class.